If you are seriously afraid of the animals in the forest, logic suggests you don't go into that forest. Problem solved.
Seriously, do your research beforehand; know what, if any, dangerous animals are known to frequent the area, their habits, and the appropriate avoidance techniques. Then plan accordingly. Ipod off; brain on!
I would only take special protective precautions in areas where Grizzly or Polar Bears are found. Fortunately for me, Polar Bears in the PNW are found only in zoos.
Black Bears are rarely predatory; they just want your food, so use common sense - keep a clean camp and use either a bear canister or a good hang. Once Yogi and Boo-Boo get your food, you would be foolish to attempt to get it back. If an overly aggressive Black Bear is known to be operating in a given area, think twice before camping there.
Cougars are not known to sneak into camp at night just to eat hikers. They are ambush predators. Suggestion - it is probably not a good idea to go for a solo run in their territory, especially with ear buds in and your ipod on.
You'll never hear a snake coming. Refer to paragraph 2.
Remember, zombies must be shot in the head and werewolves take a silver bullet. Experience has led me to believe that my hiking socks, hanging on a nearby bush, will effectively repell all living things within a 50 yard radius. Ye, though I walk through the valley of the shadow of death, I shall fear no evil, for my socks and hiking shirt are the meanest SOBs in the valley.